Three-dimensional integration may enable fabrication of highly integrated circuitry through vertical stacking of various materials and functional components. Three-dimensional integration shows promise as methodology for developing integrated structures having higher performance, higher density, higher functionality, smaller form factor, and possible cost reductions, as compared to other technologies. However, three-dimensional integration is an emerging field, and in many instances presents challenges which will need to be addressed before this becomes a viable manufacturing path.
Wafer bonding is a methodology which may have application relative to three-dimensional integration. For instance, wafer bonding may be utilized for fabrication of silicon-on-insulator (SOI) constructions, CMOS image sensors, etc.
Wafer bonding comprises the bonding of two semiconductor assemblies to one another to form a composite structure. One method of wafer bonding comprises formation of silicon dioxide surfaces across each of the assemblies which are to be bonded to another. The silicon dioxide surfaces are then placed against one another, and subjected to appropriate treatment to induce covalent bonding between the surfaces and thereby form the composite structure. The treatment utilized to induce the covalent bonding may be a thermal treatment. In some aspects, such thermal treatment may utilize a temperature in excess of 800° C. Alternatively, one or both of the silicon dioxide surfaces may be subjected to a plasma treatment prior to the thermal treatment, and in such aspects the temperature of the thermal treatment may be reduced to a temperature within a range of from about 150° C. to about 200° C. The bonding of the silicon dioxide surfaces to one another may be referred to as “hybrid bonding”.
Another technique which may be utilized during wafer bonding is to bond metal-containing materials to one another through so-called thermo-compression bonding. The thermo-compression process may comprise clamping two semiconductor assemblies to one another such that a first metal-containing material along a surface of one of the assemblies is directly against a second metal-containing material along a surface of the other of the assemblies. Subsequently, pressure may be applied through the clamping mechanism, and a temperature within a range of from about 300° C. to about 400° C. may be applied to the metal-containing materials to induce fusion between the first and second metal-containing materials.
It would be desirable to develop new methods for wafer bonding.